Details of the former Juventus striker's contract have not been released, but he will become the club's first ever Designated Player, whereby any Major League Soccer club can purchase one player who will earn wages above their salary cap.
“Since his departure from Bologna and the announcement that the he was considering an offer from the Impact, we continued to work hard at getting him to join our club,” Impact owner Joey Saputo said in a press release. "I’d like to congratulate [sporting director] Nick De Santis for this successful negotiation.
“With all of the hard work and professionalism our club has shown over the years, we have signed today a player of the highest quality.
"We promised this city and the club’s supporters a Designated Player, and we are pleased to have been able to keep that promise.”
During his time in Italy’s top flight, Di Vaio scored 142 goals in 342 games, making him one of the league’s most lethal forwards. The Rome native spent his last seasons in Italy with Bologna, and scored 10 goals and collected seven assists in 37 games in his final campaign.
“I am very proud to become a member of the Montreal Impact and to start this new phase of my career,” said Di Vaio. “I have accepted with great enthusiasm the challenge of joining an enticing championship like MLS. I am extremely eager to make the entire club proud, from the president to their supporters.”
“From a personal standpoint, I had a good feeling from our very first meeting in Bologna with the Impact president and sporting director," he added. "They made my family and I feel good about this project in Montreal.
"It was not an easy choice to leave Bologna but I hope to be able to serve a similar role in Montreal, as I am prepared to give everything I have, including my experience and leadership for my coaches, my teammates and the organisation.”
Di Vaio arrives in Montreal on Sunday and will be introduced in a press conference on Monday.